1. Field of the Invention
The present invention relates to a device for detecting an object such as a preceding vehicle driving in front of an automotive vehicle.
2. Description of Related Art
An image processing system that uses data detected by a radar has been known hitherto. For example, JP-A-9-264954 discloses a system in which an image region is searched on an image frame, using data detected by a radar such as a distance to a preceding vehicle and a position of the preceding vehicle relative to a vehicle on which the system is mounted. In this system, however, the search for the image region cannot be performed when the data from the radar become unavailable.
To cope with this problem, JP-A-11-44533 proposes a system, in which a template image is memorized when the distance data detected by a radar are available, and an image region which is closest to the memorized template image is searched on an image frame taken when the data from the radar become unavailable. The distance to the preceding vehicle is calculated based on the position thus estimated on the image frame.
In the conventional systems, however, it is difficult to accurately calculate the distance to the preceding vehicle based on an estimated position of the preceding vehicle on the image frame, because the position of the preceding vehicle moves up and down in the image frame when the vehicle makes pitching. In the conventional system disclosed in JP-A-11-44533, the distance to the preceding vehicle cannot be accurately calculated based on the memorized template image if the distance to the preceding vehicle changes during a period in which the data from the radar are not available.